Tourists visiting Brazil’s largest city for this year’s soccer World Cup may face water shortages as Sao Paulo suffers the worst drought in at least four decades.

Water levels in the Cantareira basin, which supplies almost half of the 20 million residents of metropolitan Sao Paulo, fell to 15 percent of capacity March 17, the lowest since the data series began in 1982, according to the National Water Agency’s website. The deficit of rain means rationing is inevitable and probably will last through the tournament, said Joao Simanke, a Sao Paulo-based hydrologist.

“We can’t get back the rain we missed in January and February, and March isn’t going well either,” Simanke, the former head of the Brazilian Association of Groundwater, said by telephone. “We’re going to have to save a lot of water for the World Cup because we’ll be between a rock and a hard place.”

The threat of water shortages is the latest in a series of setbacks leading up to the world’s biggest soccer competition, including cost overruns and delays at almost every one of the 12 new and refurbished stadiums. Airlines are being forced to cancel flights after authorities restricted airspace on game days while a building in Rio de Janeiro meant to house thousands of journalists won’t be ready in time for the event.

Sao Paulo will host the inaugural game and five other matches of the World Cup, which runs from June 12 to July 13.

Sao Paulo water utility Sabesp and the state government’s water department didn’t return emails requesting comment. The mayor’s office declined to comment.

Suction Pipes

The flow of water into Cantareira was 13 percent of the historic monthly average in February, according to the National Water Agency. The water level will be below the suction pipes by July, newspaper Estado de S. Paulo reported March 17, citing the Cantareira basin monitoring committee.

Sabesp will install pipes to allow it to tap the bottom of reservoirs and already is reducing the supply of water to distributors outside the metropolitan area, Estado said.

Water reservoirs that generate electricity in the country’s southeastern region are at their lowest since 2001, when the country rationed energy for several hours a day. Brazil as a result has been forced to generate more expensive power using thermoelectric plants.

To contact the reporters on this story: Raymond Colitt in Brasilia Newsroom at rcolitt@bloomberg.net; Christiana Sciaudone in Sao Paulo at csciaudone@bloomberg.net To contact the editors responsible for this story: Andre Soliani at asoliani@bloomberg.net Randall Woods